Core for undercut cup-shaped articles



Jilly 1, 193 0 PICKERING 1,769,455

CORE FOR UNDERCUT CUP SHAPED ARTICLES Filed Aug. 128; 1929 INVENTOR7/1'606/0/"6 Pi'af e/vkry BY 7 v ATTO'RNEY Patented July 1, 1930 UNITEDSTATES 00., A CORPORATION OF NEW"O RK I CORE FOR UNDERC UT CUP-SHAPEDARTICLES Application filed August 28, 1929. "SeriaiNo. 388,903.

My invention has particular reference to the problemsarising in thecasting of cupshape articles in permanent molds where the article has aninternal undercut.

Sand or other disintegrable cores have been used for the purpose, and insome instances permanent collapsible cores have been used. A permanentcore is obviously more desirable for several reasons, among which areeconomy and a resultant smoother surface to the casting formed by thecore. However, the production of collapsible cores requires an accuracyof machining and truing of parts which render such cores rela tivelyexpensive; and moreover the labor of drawing and again assembling suchcores is considerable as compared with solid cores.

In particular is this true of cup-shape articles where the internalwalls are cylindrical and have overhanging portions. Forcxaimple,-pistons forinternal combustion engines present an especialproblem by reason of the complex internal shape due to the presence ofthe wrist-pin bosses.

In-accordance with my invention I take care of the undercuts formed bythe bosses by the use of disintegrable core sections and I use a solidpermanent core section for all the rest of the casting, the sectionsbeing united with sufiicient permanency to withstand the castingpressure, and yet being easily separable after the casting operation.The permanent part constitutes the entire core of the skirt of thepiston outside of the transverse plane containing the diameters of thewrist-pin bosses, and the central portion of the remainder. manent partof the core which extends beyond the wrist-pin bosses, constitutes areduced axial extension transverse to the wristpin bosses. Thisextension, the sides of which converge, extends to the end of the coreor the inner surface of the head of the piston. On either side of theextension of the permanent core and secured thereto there aredisintegrable sand portions having a shape complementary to the undercutportion of the article. Thus, when the casting is completed, thepermanent portion of That portion of the perthe core may be withdrawn"sand portions may be loosened and removed. Y

' 'rnnonoan PICKIERING, or BATAVIA, NEW YORK, .ASS'IGNOR'nononiinnn-prn-oasr ne I shall now-describe one embodiment of myinvention in connection with the accompanying drawings in which: 1

Fig. lis a perspective of acoreembodying my invention;

Fig. 2 is a section of an internal combus-- tion engine piston withiacoreplaced therein; and Y Fig. 3 is a transverse line 3"?3 of Figure 2.

section, taken on the .The core illustrated in the drawings;-

whichis the type used in casting pistons for internal combustionengines, is adapted to be used with a permanent mold such, for example,as are used in die casting and which are well known to those skilled'inthe art. Essentially, the core consists of three parts, namely, acentral permanent part 1 and two disintegrable parts 2.

The permanent part 1' of the core is adapted to fill theinterior ofthepiston outside .the transverse plane containing the diameters of thewrist-pin bosses 3 of, the piston. The outer surface of the; part l'is,therefore, complementary to-the desired contour of the inner surface ofthe piston outside the transverseplane containing the center lines ofthe wrist-pin bosses 3. :An

axial extension '4, transverse to the bosses 3 and having convergingsldes, extendsfrom' the lower end of the permanent part land is integraltherewith. The flange 4 extends along the inside of the piston to thehead thereof; along that portion of thepiston which does not-containundercut recesses. The converging sides of the flange 4 are pro 1 videdwith undercut or dove-tail. tongues, 5

which are received in complementary grooves inthe arts 2 to unite thethree parts of the core.

his construction is-not, however, essential, as theconv'erging sides ofI the flange 4 may be smooth and the parts 2 v glued or otherwisesecured thereto..

.The parts 2 may be constructed from plaster of Paris or sand withwhicha binding agent has been mixed. The parts2 extend from the centerof the. wrist-pin bosses 3, to the head of the piston as shown. Be-

low the recesses in the parts 2 which are provided for forming thewrist-pin bosses, there are provided projections 6 which are adapted toform the undercut recesses of the piston. These recesses, below the'bosses, are necessary to properly proportion the metal in ,the piston3A diainetrical groove is provided in the lower edge of the completedcore and extends up the sides of the parts? to the lower surface otthewristsection, the contiguous faces of the sections having dove-tailinterlocking relation.

In witness whereof, I hereunto subscribe V my signature.

THEODORE PIOKERING.

pin bosses 3. The grooveis adapted to form;

a reinforcing flange 7 across the head of the piston. It is to benotedthat the parts 2 are be used for making them.- 2

The complete core is placed in the permanent mold and held in'place bythe wristidentical and therefore a single pattern may pin cores. Themolten metal is then forced in "around the'core. After the metal hascooled sufficiently the permanent part 1 of the core may be removed. Thepiston or other article is then subjected to a heat treatment which,incidentally, destroys the binding' material in the sand molds and afterwhich they may be jarred loose from the I casting.

It will be evident'to those skilled in the art that I have devised asimplified core for undercut cup-shape articles which considerablyreduces the time required for making up such cores. i

Itis obvious that various changes may be made by those skilled in theart in the illustrated embodiment oi my invention above particularlydescribed within the principle and scope of my invention as expressed ininternal undercutcomprising a permanent section-forming the entire coreoutside the undercut portion of the article and having a reduced axialextension forming the central part of the core at the undercut portionof t e article and two disintegrable core sections having ashape comlemental to the undercut portion of the article and detach ably securedto the axial extension on said A first section.

3. A core for cup-shape articles having an internal undercut comprisinga permanent section forming the entire core above the undercut a longitulnal extension forming the central part of the remainder of the core,and two' disintegrable sections for forming the undercut recesses in thearticle detachably secured to the extension on said permanent I (portionof the article and having

